Syringe gaskets (hereinafter also simply referred to as a “gasket”) are generally configured with natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber or other similar rubber materials contained as a major component, or with an elastomeric material as represented by a styrene butadiene copolymer contained as a major component.
When a rubber syringe gasket is compared with an elastomeric syringe gasket, the former normally exhibits a more excellent function in liquid tightness than the latter. However, some liquid medicines contain a component having nature to adsorb to rubber, and accordingly, when such a liquid medicine is used, the elastomeric syringe gasket is suitably used.
Note that typical syringe gaskets and syringes including the same are disclosed for example in Japanese Patent Laying-Open No. 2001-190667 (PTD 1) and Japanese Patent Laying-Open No. 2008-307237 (PTD 2).